EN 16859:2017

SLOVENSKI STANDARD
01-junij-2017
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Water quality - Guidance standard on monitoring freshwater pearl mussel (Margaritifera
margaritifera) populations and their environment
Wasserbeschaffenheit - Anleitung für das Monitoring von Populationen der
Flussperlmuschel (Margaritifera Margaritifera) und ihrer Umwelt
Qualité de l'eau - Norme guide sur le suivi des populations de moules perlières d'eau
douce (Margaritifera margaritifera) et de leur environnement
Ta slovenski standard je istoveten z: EN 16859:2017
ICS:
13.060.70 Preiskava bioloških lastnosti Examination of biological
vode properties of water
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 16859
EUROPEAN STANDARD
NORME EUROPÉENNE
February 2017
EUROPÄISCHE NORM
ICS 13.060.70
English Version
Water quality - Guidance standard on monitoring
freshwater pearl mussel (Margaritifera margaritifera)
populations and their environment
Qualité de l'eau - Norme guide sur le suivi des Wasserbeschaffenheit - Anleitung für das Monitoring
populations de moules perlières d'eau douce von Populationen der Flussperlmuschel (Margaritifera
(Margaritifera margaritifera) et de leur environnement Margaritifera) und ihrer Umwelt
This European Standard was approved by CEN on 4 December 2016.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2017 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 16859:2017 E
worldwide for CEN national Members.

Contents Page
European foreword . 5
Introduction . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Monitoring and assessing the condition of a Margaritifera population. 12
4.1 Requirements for a sustainable Margaritifera population. 12
4.1.1 General . 12
4.1.2 Monitoring . 12
Table 1 — Checklist of monitoring recommended on mussel attributes in rivers with
Margaritifera . 13
4.2 Training and quality assurance for pearl mussel survey and assessment. 14
4.2.1 Pearl mussel survey . 14
4.2.2 Training manuals . 15
4.2.3 Data entry and validation . 15
4.2.4 Licences . 15
5 Monitoring the environmental conditions needed to support Margaritifera
margaritifera populations . 15
5.1 General . 15
5.2 Fish hosts . 16
5.2.1 Fish host species . 16
Table 2 — Checklist of monitoring recommended on fish hosts in rivers with Margaritifera . 16
5.2.2 Barriers to fish migration . 17
5.2.3 Host suitability . 17
5.3 Water quality . 17
5.3.1 General . 17
5.3.2 Phosphorus. 17
5.3.3 Nitrogen, including ammonia . 17
5.3.4 BOD / dissolved oxygen . 18
5.3.5 pH . 18
5.3.6 Calcium. 18
5.3.7 Alkalinity . 18
5.3.8 Electrical conductivity . 18
5.3.9 Temperature . 18
5.3.10 Contaminants . 19
5.3.11 Turbidity, suspended solids . 19
Table 3 — Checklist of monitoring recommended on water quality parameters in rivers
with Margaritifera . 19
5.3.12 Biotic indicators of water quality . 20
Table 4 — Checklist of monitoring recommended on biotic indicators in rivers with
Margaritifera . 21
5.4 Hydromorphology. 21
5.4.1 Monitoring requirements . 21
Table 5 — Checklist of monitoring recommended on flow and physical environmental
parameters in rivers with Margaritifera. 21
5.4.2 Flow . 22
5.4.3 Physical habitat structure . 23
Table 6 — Clast sizes relevant to Margaritifera habitat (according to EN ISO 14688-1:2002,
Table 1) . 24
5.4.4 Substrate quality . 24
5.4.5 Substrate stability . 25
5.4.6 Trees and wood . 25
5.4.7 Instream modifications . 25
6 Monitoring environmental pressures . 25
Table 7 — Checklist of environmental pressures recommended for risk-based monitoring
in rivers with Margaritifera . 26
7 Information needed to assess plans or projects on rivers with Margaritifera . 27
Table 8 — Checklist of questions that should be addressed to ensure that plans or projects
do not damage Margaritifera populations . 27
Annex A (informative) Background information on the environmental characteristics
important for maintaining populations of Margaritifera margaritifera . 29
A.1 Fish hosts . 29
A.1.1 Fish host species . 29
A.1.2 Barriers to fish migration . 29
A.1.3 Host suitability and stocking practices . 29
A.2 Water quality . 30
A.2.1 Phosphorus . 30
A.2.2 Nitrogen, including ammonia . 30
A.2.3 BOD /dissolved oxygen . 30
A.2.4 pH . 30
A.2.5 Calcium . 31
A.2.6 Alkalinity . 31
A.2.7 Electrical conductivity . 31
A.2.8 Temperature . 32
A.2.9 Contaminants . 32
A.2.10 Turbidity, suspended solids . 32
A.3 Biotic indicators of water quality . 33
A.3.1 Macroinvertebrates . 33
A.3.2 Diatoms . 33
A.3.3 Filamentous algae . 33
A.3.4 Macrophytes . 33
A.4 Hydromorphology . 34
A.4.1 Flow . 34
A.4.2 Physical habitat structure . 34
A.4.3 Substrate quality . 35
A.4.4 Substrate stability . 36
A.4.5 Trees and wood . 36
A.4.6 Instream modifications . 36
A.5 Biotic factors and other interactions . 37
A.5.1 Pressures and interferences . 37
A.5.2 Human interference . 37
A.5.3 Invasive non-native species . 37
A.5.4 Non-native fish . 37
A.5.5 Non-native molluscs . 37
A.5.6 Non-native crayfish . 38
A.5.7 Non-native plants . 38
A.5.8 Non-native mammals . 38
Annex B (informative) Targets for assessing whether Margaritifera populations are in
favourable condition . 39
Table B.1 — Criterions and targets to achieve sustainable Margaritifera populations . 39
Annex C (informative) Range of environmental conditions supporting sustainable
populations of Margaritifera . 40
Table C.1 — Range of environmental conditions supporting sustainable populations of
Margaritifera (with referenced work on which levels are based) . 40
Bibliography . 44
European foreword
This document (EN 16859:2017) has been prepared by Technical Committee CEN/TC 230 “Water
analysis”, the secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by August 2017, and conflicting national standards shall
be withdrawn at the latest by August 2017.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
Introduction
This European Standard provides guidance on monitoring populations of freshwater pearl mussel
Margaritifera margaritifera and the environmental features on which this species depends. Pearl
mussels are endangered throughout their Holarctic range as a result of intensive land-use, pollution,
river engineering, abstraction, declining populations of host fish, and exploitation by pearl fishers [1],
[2], [3]. Throughout this document, use of the term Margaritifera refers only to the species
Margaritifera margaritifera (Linnaeus, 1758). Within the EU, Margaritifera is protected under national
legislation as well as by the EC Habitats Directive (Council Directive 92/43/EEC) which requires Special
Areas of Conservation to be designated to safeguard this species. The presence of a population of
Margaritifera with full juvenile recruitment is the sign of a healthy functioning river [4].
Margaritifera has a well-documented but complicated life history, with a larval glochidial stage
dependent on a salmonid host. The larvae encyst within the host fish gills following release of glochidia
in summer or early autumn. There they overwinter and grow before dropping off in the following
spring or early summer. The few that survive initially remain buried in the river-bed substrate for
several years where they interact with interstitial water. Older mussels typically have their siphons
exposed to filter within the open water. The glochidial and juvenile stages are more demanding of a
high-quality environment than adult mussels, emphasizing the importance of defining and maintaining
appropriate ecological conditions for the young stages [5].
Margaritifera lives for an unusually long time – over 100 years in much of its range – but life spans can
be much shorter at the southern extreme of its range and much longer at the northern extreme. A lack
of recruitment of young mussels leads to populations becoming unsustainable, but these problems can
be masked by the continued survival of older mussels for many years long after successful recruitment
has ended. The requirement for a host salmonid fish to carry the mussel larval stage presents an added
challenge in maintaining the condition of freshwater pearl mussel populations.
Although Margaritifera is highly demanding in river substrate and water quality, it occurs in a wide
range of catchments from small, siliceous, oligotrophic rivers, often with a lake upstream, to large
lowland mineral systems. This standard strives to encompass the range of latitudinal and geological
factors that affect Margaritifera across its range. It is essential to take into consideration the unique
pressures on each individual population when setting priorities for monitoring.
NOTE A limited number of key references are given in the Bibliography. A comprehensive list can be
consulted by using the following link to the website of the Freshwater Biological Association –
http://www.fba.org.uk/cen-pearl-mussel-standard-development-reference-list
The applications of the standard include the provision of site-level data that will contribute to reporting
under the Habitats Directive, Article 17, undertaking environmental impact assessment, and restoring
pearl mussel populations.
WARNING —Safety issues are paramount when surveying rivers. Surveyors should conform to
EU and national Health and Safety legislation, and any additional guidelines appropriate for
working in or near rivers.
IMPORTANT — Freshwater pearl mussel surveys are carried out under licence, and the methods
used should be fully compliant with any conditions imposed.
1 Scope
This European Standard provides guidance on methods for monitoring freshwater pearl mussel
(Margaritifera margaritifera) populations and the environmental characteristics important for
maintaining populations in favourable condition. The standard is based on best practice developed and
used by Margaritifera experts in Europe, and describes approaches that individual countries have
adopted for survey, data analysis and condition assessment. While it is recommended that the causes
for pearl mussel decline should be urgently investigated, standard methods for restoring populations
are beyond the scope of this document.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
EN ISO 14688-1:2002, Geotechnical investigation and testing - Identification and classification of soil -
Part 1: Identification and description (ISO 14688-1:2002)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
acoustic doppler current profiler
ADCP
sonar device that produces a record of water current velocities for a range of depths
3.2
aquatic macrophyte
larger plant of fresh water which is easily seen with the naked eye, including all aquatic vascular plants,
bryophytes, stoneworts (Characeae) and macro-algal growths
Note 1 to entry: This definition includes plants associated with open water or wetlands with shallow water.
[SOURCE: EN 14614:2004, definition 2.1]
3.3
bankfull
maximum point on banks at which floods are held within the channel before spilling over onto the
floodplain
[SOURCE: EN 14614:2004, definition 2.5]
3.4
baseline survey
first survey of environmental or biological features by which progress towards rehabilitation or
continuing decline can be monitored by subsequent surveys
3.5
bathyscope
bucket with a transparent bottom used for viewing freshwater pearl mussels on the river bed
3.6
biochemical oxygen demand after 5 days
BOD
mass concentration of dissolved oxygen consumed under specified conditions by the biochemical
oxidation of organic and/or inorganic matter in water after 5 days
Note 1 to entry: For the purposes of this document, “biochemical oxidation” is taken to mean “biological
oxidation”.
[SOURCE: ISO 5815-1:2003, definition 3.1 modified]
3.7
brooding period
length of time that glochidia remain within the body of a gravid pearl mussel
3.8
colmation
blockage of stream-bed interstitial spaces by the ingress of fine sediments and organic material
3.9
compaction
consolidation of the river bed through physical, chemical or biological processes
[SOURCE: EN 14614:2004, definition 2.10]
3.10
concretion
hard, compact mass of sedimentary rock formed by the precipitation of mineral cement within the
spaces between the sediment grains
3.11
culvert
arched, enclosed or piped structure constructed to carry water under roads, railways and buildings
[SOURCE: EN 15843:2010, definition 3.8]
3.12
ecological quality ratio
EQR
ratio between the value of the observed biological parameter for a given surface water body and the
expected value under reference conditions
3.13
encystment
process in which pearl mussel glochidia attach to the gills of their salmonid hosts
3.14
eutrophication
process by which a body of water acquires an overabundance of nutrients, especially phosphates and
nitrates, leading to increased growth of algae and macrophytes
3.15
favourable condition
condition of a population compatible with contributing to 'favourable conservation status'
Note 1 to entry: As defined in Article 1 of the Habitats Directive”:- population dynamics data on the species
concerned indicate that it is maintaining itself on a long-term basis as a viable component of its natural habitats,
and- the natural range of the species is neither being reduced nor is likely to be reduced for the foreseeable future,
and- there is, and will probably continue to be, a sufficiently large habitat to maintain its populations on a long-
term basis.”
3.16
filter feeding
process by which pearl mussels feed by straining suspended matter and food particles from water,
typically passing the water over a specialized filtering structure
3.17
flow duration curve
graphical representation of a ranking of all the flows in a given period, from the lowest to the highest,
where the rank is the percentage of time the flow value is equalled or exceeded
Note 1 to entry: These curves may be derived for flows in any time interval, such as daily flows, monthly flows
or annual flows
3.18
fluvial audit
method for assessing the condition of a river and its associated human pressures, using information
from field survey, remote sensing, historical and recent maps, scientific literature and other sources
3.19
functionally extinct (not currently viable)
pearl mussel population that is incapable of sustaining itself owing to a lack of juvenile recruitment
3.20
glide
moderately-flowing water with undisturbed surface other than occasional swirls or eddies, and with
constant depth across part of the channel
[SOURCE: EN 14614:2004, definition 2.17]
3.21
glochidium (plural ‘glochidia’)
larva of Margaritifera
3.22
glochidial release
process by which gravid pearl mussels release glochidia into the water
3.23
gravid
carrying eggs or developing young
3.24
hydromorphology
physical and hydrological characteristics of rivers including the underlying processes from which they
result
[SOURCE: EN 14614:2004, definition 2.18]
3.25
hyporheic zone
spatio-temporally dynamic ecotone between the surficial benthic sediments and the underlying aquifer
3.26
interstitial habitat
area occupied by aquatic organisms in the spaces between sediment particles
3.27
otoscope
instrument designed for examining the interior of the ear but in the context of this standard used to
investigate brooding in freshwater pearl mussels
3.28
penetrometry
method for assessing the resistance of the river-bed substrate in situ using a standard cone or disc
penetrometer
3.29
pool
habitat feature characterized by distinctly deeper parts of the channel that are usually no longer than
one to three times the channel’s bankfull width, and where the hollowed river bed profiles are
sustained by scouring
[SOURCE: EN 14614:2004, definition 2.24]
3.30
recruitment
survival of juvenile pearl mussels and their addition to a population
3.31
redox potential
Eh
tendency of a substance to gain or lose electrons
Note 1 to entry: In the context of this standard, redox measurements of the stream-bed water at the typical
depth of juvenile mussels are used as indicators of oxic (high Eh) or anoxic (low Eh) conditions.
3.32
reference river
river containing viable population of pearl mussels, where the associated environmental characteristics
can be used to help define the species’ requirements
3.33
reproductively viable
able to maintain a self-sustaining population without the addition of new genetic material from outside
the system
3.34
riffle
fast-flowing shallow water with distinctly broken or disturbed surface over gravel/pebble or cobble
substrate
[SOURCE: EN 14614:2004, definition 2.28]
3.35
riparian zone
area of land adjoining a river channel (including the river bank) capable of directly influencing the
condition of the aquatic ecosystem (e.g. by shading and leaf litter input)
Note 1 to entry: In this European Standard, the term ‘riparian zone’ does not include the wider floodplain.
[SOURCE: EN 14614:2004, definition 2.29]
3.36
salmonid host
essential host for pearl mussel glochidia, in Europe usually Atlantic salmon (Salmo salar) or brown
trout (Salmo trutta)
3.37
salt bridge
device containing a chemically inert electrolyte which is used to increase electrical conductivity locally
3.38
shear stress
measure of the force of friction caused by water flowing around a submerged surface or object
3.39
turbidity
reduction of transparency of a liquid caused by the presence of undissolved matter
[SOURCE: ISO 6107-2:2006, definition 145]
3.40
wade gauging
wading across the river taking measurements at regular intervals (e. g. depth, velocity)
3.41
woody material
material that falls into rivers and streams, ranging in size from leaf fragments (fine woody material) to
branches or whole trees (coarse woody material)
4 Monitoring and assessing the condition of a Margaritifera population
4.1 Requirements for a sustainable Margaritifera population
4.1.1 General
Monitoring the condition of Margaritifera populations is carried out in three ways:
a) direct monitoring of the condition of the pearl mussel population;
b) direct monitoring of the condition of pearl mussel habitat;
c) monitoring indicators of the state of the pearl mussel environment, using databases or by new
survey (b) and c) are covered in Clause 5).
Monitoring Margaritifera populations is needed for a wide range of purposes. The purpose of the
investigation should determine the direct and indirect aspects of the environment that need to be
considered. The following main types of investigation can be distinguished: detailed baseline
monitoring; routine surveillance; investigating the causes of decline; ecological impact assessment;
monitoring the effectiveness of management measures.
As viable Margaritifera populations are mainly found in undisturbed streams, water quality and other
relevant data have rarely been collected and in many cases serious problems had already progressed
before relevant data collection commenced. The first studies in a river with Margaritifera are therefore
not normally a baseline of reference conditions, but a first survey by which progress towards
rehabilitation or continuing decline can be monitored in subsequent surveys.
Targets for assessing whether Margaritifera populations are in sustainable condition are given in
informative Annex B.
4.1.2 Monitoring
Adequate information on Margaritifera populations in good quality habitats and with successful
recruitment of young mussels is essential if the aim of returning declining pearl mussel populations to
favourable condition is to be met.
Monitoring should include a suite of samples and surveys recommended in Table 1 as a baseline. Once a
baseline is established, the frequency of monitoring should be based on an assessment of risk to the
population, with some aspects needing to be carried out at a higher frequency than others. Where
negative pressures are apparent, investigative monitoring may be required to establish their cause.
Attributes of pearl mussel populations that should be monitored are shown in Table 1.
Mussel surveys should be carried out by wading using a bathyscope or by snorkelling/SCUBA diving in
the river. Mussels should be counted in river stretches or by estimation using transects along or across
the river and extrapolation to assess distribution and density. Standard methods developed for the
country in which the survey is carried out should be used. Fixed repeatable monitoring transects should
be established to assess changes in mussel distribution and density, substrate composition, and the
cover of filamentous algae, macrophytes and fine sediment.
Population structure should be assessed by measuring the lengths of mussels including those mussels
buried within the substrate.
NOTE 1 In some countries, standard methods do not include investigations of buried mussels.
A series of quadrats builds up a profile of the recent reproductive success in the population. It is
imperative that demographic counts are carried out in very stable habitat, that measurements are made
rapidly, and that mussels and substrate are replaced carefully before moving on to the next site. To
avoid damage to the population, the number of quadrats examined should be minimal, adequately
spaced apart, and the work carried out by well trained and experienced workers during appropriate
low-flow and low-turbidity conditions. Measurements should be made at random within areas where
suitable mussel habitat is found. These data should form a series of separate size profiles that represent
the population within the river. For repeat surveys for monitoring purposes it is appropriate to return
to the same general areas. For each population profile, at least 250 mussels should be measured. In
small populations this may not be possible, and measurements may need to be combined from different
parts of the river. Ideally, quadrats should be linked to permanent transects by being close to but not
immediately on or adjacent to them.
NOTE 2 This standard is principally concerned with surveying mussels in relatively shallow water. However,
surveys of mussels in deep water can also be undertaken using an underwater camera or by diving.
Table 1 — Checklist of monitoring recommended on mussel attributes in rivers with
Margaritifera
Aspect Method Output (units) Notes
Distribution Wading or snorkelling Map Once thoroughly to create a
/SCUBA survey counts baseline with checks during 6
year survey
Population Wading or snorkelling/ Number of mussels Every 6 years, more frequently
density SCUBA survey counts 2 if needed for investigative
per m
(including transects) monitoring (normally through
repeating transect counts).
Individual Quadrat analysis Mussel measurement 5 mm class size grouping is
mussel size (mm) recommended. Demography
should be assessed every 6
years or more frequently for
investigative monitoring.
Population age Analysis of growth rates Growth curve (mm Where juveniles and young
structure per year) mussels are present, age–size
relationships should be
established, particularly the
range of sizes for mussels
under 5 years and under 20
years for mussels with a life
span of about 100 years. For
longer and shorter life spans,
the age–size relationships will
vary accordingly. (Note that
removing mussels to establish
age structure could be
damaging if repeated too
frequently.)
Brooding levels Visual, sub-sample of Age (%) of surveyed To be undertaken where no
mussel adults checked mussels with other evidence of recruitment
using otoscope by evidence of brooding, has been found.
trained expert based on a sample of
20 individuals
4.2 Training and quality assurance for pearl mussel survey and assessment
4.2.1 Pearl mussel survey
Surveyor training is essential to ensure consistency, accuracy and precision. Surveyors need to
understand the biology of the species sufficiently to appreciate the reasons for the methods used and
the need for care in their application to avoid damage to pearl mussels.
Training should be structured to cover the level of survey required, from non-invasive counts of adults
to specialist demographic quadrat analysis. Where relevant, a qualification in snorkelling / SCUBA
diving should precede Margaritifera survey training. Although counting adult mussels can be taught to a
wide range of surveyors, handling adults and juveniles should only be carried out by experts. In general,
the more experienced that surveyors are the more likely they are to carry out an accurate survey. If
survey experience is infrequent, regular refresher courses are recommended.
Content of training should include:
a) health and safety education relevant to mussel survey;
b) monitoring mussels without damaging them;
c) planning surveys, including issues of access and permission;
d) carrying out full mussel counts and population estimates, including wading with a bathyscope and
snorkel/SCUBA survey;
e) setting out permanent monitoring transects and how to survey and relocate them, including the use
of photography;
f) completing recording forms accurately;
g) carrying out juvenile searches and demographic profiles (expert training);
h) reporting survey results and compiling licence returns;
i) mapping mussel habitats;
j) gathering data on river corridor and land use.
Training should:
k) ideally incorporate a certification system;
l) provide regular refresher courses;
m) be carried out over the range of river types that will be encountered in the country or area covered
by the certification;
n) be carried out in rivers that require wading with a bathyscope and rivers that demand snorkel /
SCUBA survey;
o) be fully supported by manuals of techniques.
Before certification, the course participants should carry out a trial survey. Procedures should be put in
place to test the results obtained by different surveyors on the same stretches of river. If a surveyor
consistently records results that vary from those recorded by experts, the problem should be rectified
by additional training, and certification should only be provided when survey results are deemed to be
accurate.
4.2.2 Training manuals
Training manuals should be designed to support the objectives of this standard and incorporate
national requirements. Manuals should include general background, unambiguous information on how
to carry out surveys, accurate descriptions of the features to be recorded, and guidance on the format in
which the data are to be maintained and presented. Text should be supported by illustrative material
(e.g. photographs, videos, DVDs, CDs) to help describe survey details.
4.2.3 Data entry and validation
It is important that no errors occur when transferring data from field sheets to databases and
Geographical Information Systems (GIS). Suitable quality assurance methods should be used, such as
double entry of data into databases by two different operators followed by tests to ensure the results
are identical. Data corruption can occur when systems are updated or during information transfer;
some form of checking procedure is required following such changes. Sensitive data on Margaritifera
populations should only be released according to national protocols on endangered species.
4.2.4 Licences
Margaritifera surveys are carried out under licence, and the methods used should be fully compliant
with any conditions imposed. It is essential to maintain accurate information on the distribution and
status of Margaritifera. A survey licence is normally provided on the understanding that data gathered
are provided to the competent authority.
5 Monitoring the environmental conditions needed to support Margaritifera
margaritifera populations
5.1 General
The assessment of water quality, hydromorphology, fish and macroinvertebrate features in pearl
mussel rivers should be carried out by trained personnel. National protocols should always be used, and
surveyors shall ensure that they obtain the appropriate licences before starting work.
High water quality is vitally important in maintaining sustainable Margaritifera populations [6].
Together with direct damage, flow changes and sedimentation, a decline in water quality is often
responsible for the loss of Margaritifera recruitment and ultimately for the extinction of populations. To
assist clarity in presentation, this standard describes the ecological requirements of Margaritifera in
three separate sections: fish hosts, water quality, and hydromorphology (including flow and habitat
structure). However, these factors do not act in isolation from each other and their combined effects
need to be taken into account when determining the requirements of a specific pearl mussel population.
In addition, it is important to assess the requirements of Margaritifera populations in a way that takes
account of the differences betwee
...